For a storage device that has a file system, data that is written to the storage device must be atomic. Atomicity refers to a complete operation of a transaction, that is, data related to the transaction must be completely written or not written. In the prior art, data atomicity is guaranteed in a disk. Data in a cache is generally not atomic, that is, only data stored in a disk is considered as reliable data and can be provided for a host. In general, if a storage device has a fault, data needs to be restored from a cache and data in the cache is then written to a disk. When the data in the cache is written to the disk, a log means is used to guarantee that the data written to the disk is atomic. When a host sends, to the storage device, an access request for accessing the data, the atomic data needs to be first acquired from the disk, and then provided for the host. This prolongs a time for processing the access request sent by the host.